This invention relates generally to incinerator systems for the abatement of process emissions and more specifically to a novel valve for the control of fluid flow to and from a regenerative incinerator.
Process emissions often contain combustible contaminants that, if released to atmosphere, have the potential of polluting the environment. Incinerators increase the temperature of such process emissions to a temperature above the ignition temperature of the contaminants therein so as to oxidize the contaminants.
One problem that materially effects the efficiency of such incinerators is leakage of contaminated emissions past the relatively large flow control valves required for control of fluid flow to and from the incinerators. The flow control valves in the open mode of operation direct the emissions into one or more regenerators thence to high temperature combustion chambers. Concomitantly, other flow control valves in the closed mode of operation block the flow of contaminated emissions to regenerators that are vented to atmosphere or are being purged of contaminants. Leakage past the flow control valves operating in the latter mode seriously compromises incinerator system efficiency, and creates potential purity problems with the incinerator exhaust emission.
Typical backflow preventers have been used in the past for pressurized environments such as heating systems and water supply systems to prevent the backflow (i.e., reversal of normal flow) of possible contaminants into uncontaminated flow lines. However, backflow preventers are constructed in complex, multiple valve stages. Thus, backflow preventers add excessive hardware to the system at an attendant high cost. Simpler known valve arrangements, such as a ball valve with associated venting, are not large enough to adequately function as incinerator flow control valves and/or cannot be feasibly constructed of materials able to operate over typical incinerator temperature ranges of 50.degree. F. to 1000.degree. F. (.about.18.degree. C. to 540.degree. C).